Labour will try to undermine David Cameron's "vote for change" pitch at the general election by warning that a Conservative government would "turn back the clock" rather than take Britain forward.

Ministers have agreed to highlight Tory plans to end the ban on fox hunting, cut inheritance tax and reward marriage in the tax system in Labour's election campaign in an attempt to question Mr Cameron's credentials as a moderniser.

"We have to answer the 'change to what?' question because the Tories won't," one minister said. "We will put the spotlight on the areas where a Tory government would go backwards."

In a softly-softly approach, Tory parliamentary candidates have been advised by Conservative Campaign Headquarters to keep a low profile on hunting in order not to alienate voters who support the ban, which was introduced by Labour in 2004. They have been encouraged not to take part in surveys by newspapers or polling firms about the issue.

But a grass-roots campaign by opponents of hunting, who have asked individual MPs and candidates their views by writing to them at a local level, has revealed a stark contrast between the two main parties. Of the 122 Tory MPs and candidates who responded, 97 said that they did not support the ban while only 16 did and another nine replied "don't know". Of the 295 Labour MPs and candidates who responded, 284 supported the ban, 10 opposed it and there was one "don't know".

The findings of the Back the Ban campaign's survey have persuaded Labour to make hunting an election issue even though the party will risk Tory accusations of reverting to "class war". Mr Cameron has promised a free vote on hunting if he becomes prime minister and the responses suggest the Commons would vote to lift the ban if the Tories won a majority.

Hilary Benn, the Environment Secretary, who launched the campaign in December, said yesterday: "This information shows that the Tories are very far from the supposedly modern, compassionate party that David Cameron wants you to see. It seems that the majority of Tories want to spend government time legalising a so-called sport in which the participants allow dogs to rip other animals apart, even though a majority of the British people support the hunting ban."

The 2004 Hunting Act made the hunting of all wild mammals using dogs an offence and banned hare coursing, but did not prevent people from riding with dogs if they remained within the law. The Tories describe the Act as ineffective and unworkable, saying there have been few successful prosecutions. Mr Cameron has argued that such a bad law should be repealed.

The Tory leader reaffirmed his commitment to radical change in a speech at his party's spring conference on Sunday. Tory strategists say the party will make "change" its main pitch, spelling out their key policies while asking voters whether they want "another five years of Gordon Brown".

Despite the Tories' pledge to cut the public deficit faster than Labour, Mr Cameron said he would spell out before the election how marriage would be rewarded in the tax system. A rise in the threshold for inheritance tax to £1m has been promised by the following general election.